Light-emitting device and electronic apparatus

ABSTRACT

A light-emitting device includes: a substrate; a plurality of light-emitting elements which is formed on the substrate and each of which has an anode partitioned by an insulating pixel partition wall, a cathode, and an organic light-emitting layer interposed therebetween and emits light by an electric field generated by the anode and the cathode; a first organic buffer layer that is formed by applying an organic compound and hardening the organic compound and covers a region larger than the region in which the plurality of light-emitting elements are formed; a second organic buffer layer that is that is formed by applying an organic compound and hardening the organic compound and is arranged above the substrate with the first organic buffer layer interposed therebetween so as to cover the plurality of light-emitting elements; and a gas barrier layer that is formed of an inorganic compound, covers a region larger than the region in which the first and second organic buffer layers are formed, and protects the plurality of light-emitting elements from air. In the light-emitting device, a region of the substrate overlapping the first organic buffer layer is not completely matched with a region of the substrate overlapping the second organic buffer layer.

This is a Continuation of application Ser. No. 11/470,483 filed Sep. 6,2006. This application also claims priority to Japanese PatentApplication No. 2005-336651, filed Nov. 22, 2005. The disclosure of theprior applications is hereby incorporated by reference herein in itsentirety.

BACKGROUND

1. Technical Field

The present invention relates to a technique for sealing a thin film ofa light-emitting element.

2. Related Art

As one type of light-emitting elements, there is an organic EL(electroluminescent) element that has a multilayered structure of twoelectrodes and a thin organic light-emitting film, formed of an organiccompound, interposed between the two electrodes and emits light byexcitation due to an electric field generated between the twoelectrodes. A sealing process is performed to prevent an organiclight-emitting material and a cathode, which includes an electroninjection layer formed of, for example, calcium, magnesium, or aluminumcomplex, from deteriorating. As sealing techniques, a thin-film sealingtechnique for covering organic EL elements with an excessively thininorganic compound film has been known (see JP-A-9-185994,JP-A-2001-284041, JP-A-2000-223264, and JP-A-2003-17244). In thesetechniques, the inorganic compound film serves as a gas barrier layerthat prevents the infiltration of air.

In the thin-film sealing technique, in order to cover the organic ELelements, a planarizing layer formed of an organic compound, such as anorganic buffer layer, is formed on the surfaces of cathodes of aplurality of light-emitting elements and on pixel partitions toplanarize uneven portions formed by the cathodes and the pixelpartitions, and then a gas barrier layer formed of an inorganic compoundis formed thereon. However, in the gas barrier layer having theabove-mentioned structure, stress concentrates on the edge of theorganic buffer layer (a rising portion of the organic buffer layer).When remarkable stress concentration occurs, the gas barrier layer maybe cracked or peeled off. Further, when a gas barrier layer is formed ofan inorganic compound, such as silicon compound having transmittance andhigh moisture-resistance, the inorganic compound layer has density andelastic modulus (Young's modulus) higher than those of an organiccompound layer. Accordingly, a crack may occur due to the stressconcentration.

If the gas barrier layer cracks or is peeled off, moisture contained inatmospheric air is infiltrated into the organic EL elements, whichcauses the sealing property (in particular, coatability for minuteforeign materials not purified by a clean room) of the organic ELelements to significantly deteriorate. This causes early deteriorationof the organic EL elements, which will be necessarily solved. When a gasbarrier film is composed of an organic compound film having lowelasticity to prevent the stress concentration, or when the gas barrierlayer is formed with a constant thickness to prevent the stressconcentration, the gas barrier layer is not cracked or peeled off, but asufficient sealing property is not obtained, which will cause earlydeterioration of the organic EL elements.

SUMMARY

An advantage of some aspects of the invention is that it provides alight-emitting device capable of sufficiently sealing light-emittingelements with a gas barrier layer that is prevented from being crackedor peeled off and an electronic apparatus including the light-emittingdevice.

According to an aspect of the invention, a light-emitting deviceincludes: a substrate; a plurality of light-emitting elements which isformed on the substrate and each of which has an anode partitioned by aninsulating pixel partition wall, a cathode, and an organiclight-emitting layer interposed therebetween and emits light by anelectric field generated by the anode and the cathode; a first organicbuffer layer that is formed by applying an organic compound andhardening the organic compound and covers a region larger than theregion in which the plurality of light-emitting elements are formed; asecond organic buffer layer that is that is formed by applying anorganic compound and hardening the organic compound and is arrangedabove the substrate with the first organic buffer layer interposedtherebetween so as to cover the plurality of light-emitting elements;and a gas barrier layer that is formed of an inorganic compound, coversa region larger than the region in which the first and second organicbuffer layers are formed, and protects the plurality of light-emittingelements from air. In the light-emitting device, a region of thesubstrate overlapping the first organic buffer layer is not completelymatched with a region of the substrate overlapping the second organicbuffer layer. The organic compound is a compound having a carbonskeleton as a basic structure.

A large step difference occurs in a plurality of light-emitting elementscomposed of insulating pixel partitions, a large number of anodes formedin regions surrounded by the pixel partitions, and a cathode formedthereon. When a gas barrier layer formed of an inorganic compound isdirectly adhered to the cathode, a large step difference occurs in thegas barrier layer, and the gas barrier layer is cracked or peeled off bystress concentration. In order to prevent the gas barrier layer frombeing cracked or peeled off, it is effective to apply an organiccompound on uneven portions, which are a plurality of light-emittingelements, and harden the organic compound to form an organic bufferlayer for planarizing the surface, before the gas barrier layer isformed, as in the light-emitting device according to this aspect. Alarge amount of organic compound is applied to form an organic bufferlayer having a sufficiently large thickness to fill up the step portion,thereby substantially planarizing the gas barrier layer. It is alsopossible to release stress concentration on a rising portion of the gasbarrier layer. However, in order to improve the flatness of the organicbuffer layer, it is necessary to apply a liquid material having highviscosity to form an organic buffer layer with a large thickness. Inthis case, surface tension increases, causing the angle of the edge ofthe organic buffer layer to excessively increase. That is, the riseangle of the gas barrier layer excessively increases, and thus aconsiderable amount of stress concentrates on a rising portion of thegas barrier layer.

In order to solve these problems, in the light-emitting device accordingto the above-mentioned aspect of the invention, the organic buffer layerhas a two-layer structure, and a region in which the first organicbuffer layer is formed is not completely matched with a region in whichthe second organic buffer layer is formed. Since the organic bufferlayer has a two-layer structure, the thickness of each layer is smallerthan that of the organic buffer layer having a single-layer structure.Therefore, the angle of an edge portion of each layer is smaller thanthat of an edge portion of the organic buffer layer having thesingle-layer structure. However, since the region in which the firstorganic buffer layer is formed is not completely matched with the regionin which the second organic buffer layer, a rise angle of the gasbarrier layer slightly increases in a part of or the entire risingportion of the gas barrier layer. That is, the gas barrier layer of thelight-emitting device is prevented from being cracked or peeled off.Therefore, according to the light-emitting device of this aspect, it ispossible to sufficiently seal the light-emitting elements with the gasbarrier layer that is prevented from being cracked or peeled off.

In the light-emitting device according to this aspect, the region inwhich the second organic buffer layer is formed may be larger than theregion in which the first organic buffer layer is formed, or the regionin which the first organic buffer layer is formed may be larger than theregion in which the second organic buffer layer is formed.

In the former light-emitting device, the first organic buffer layer mayinclude a first constant portion that has a constant thickness andcovers a region larger than the region in which the plurality oflight-emitting elements are formed, and a first edge portion thatsurrounds the first constant portion and is tapered off toward the edgethereof. In addition, the second organic buffer layer may include asecond constant portion that has a constant thickness and covers aregion larger than the region in which the plurality of light-emittingelements are formed, and a second edge portion that surrounds the secondconstant portion and is tapered off toward the edge thereof. Preferably,the second constant portion and the second edge portion overlap thefirst constant portion, and the thickness of the first constant portionis smaller than that of the second constant portion. The term ‘constant’means ‘being substantially constant’. More specifically, in a case inwhich the height of the pixel partition is 2 μM and a step difference ofa light-emitting region is 2 μm, when the thickness of the organicbuffer layer above the pixel partition is about 3 μm and the thicknessof the organic buffer layer in a portion in which the pixel partition isnot provided (a light-emitting portion) is about 5 μm, the surface ofthe organic buffer layer can be said to be substantially flat. Thethickness of the organic buffer layer depends on whether the pixelpartition exists or not, and a substantially flat portion of the organicbuffer layer is defined as a constant portion.

According to this light-emitting device, the second organic bufferlayer, which is an upper layer and has a small covering region, isthicker than the first organic buffer layer, which is a lower layer andhas a large covering region. Therefore, even when the total thickness ofthe first and second organic buffer layers sufficiently increases inorder to improve the sealing property of a plurality of light-emittingelements, the rise angle of the gas barrier layer is equal to the angleof the first edge portion of the first organic buffer layer having asmaller thickness. Since the second constant portion and the second edgeportion overlap the first constant portion, the gas barrier layer issequentially arranged along the first edge portion and the second edgeportion in the rising portion thereof. Therefore, even when thethickness of the second organic buffer layer, which is an upper layerand a small size, is large and the angle of the second edge portion islarge, the gas barrier layer gradually rises. In this way, it ispossible to sufficiently increase the total thickness of the first andsecond organic buffer layers covering a region in which the plurality oflight-emitting elements are arranged, while slightly increasing the riseangle of the gas barrier layer. Thus, it is possible to prevent the gasbarrier layer from being cracked or peeled off, and to further improvethe sealing property of the light-emitting elements.

In the latter light-emitting device, the first organic buffer layer mayinclude a first constant portion that has a constant thickness andcovers a region larger than the region in which the plurality oflight-emitting elements are formed, and a first edge portion thatsurrounds the first constant portion and is tapered off toward the edgethereof. In addition, the second organic buffer layer may include asecond constant portion that has a constant thickness and covers aregion larger than the region in which the plurality of light-emittingelements are formed, and a second edge portion that surrounds the secondconstant portion and is tapered off toward the edge thereof. Preferably,the first constant portion and the first edge portion overlap the secondconstant portion, and the thickness of the second constant portion issmaller than that of the first constant portion.

According to this light-emitting device, the first organic buffer layer,which is a lower layer and has a small covering region, is thicker thanthe second organic buffer layer, which is an upper layer and has a largecovering region. Therefore, even when the total thickness of the firstand second organic buffer layers sufficiently increases in order toimprove the sealing property of a plurality of light-emitting elements,the rise angle of the gas barrier layer is equal to the angle of thesecond edge portion of the second organic buffer layer having a smallerthickness. Since the first constant portion and the first edge portionoverlap the second constant portion, the gas barrier layer issequentially arranged along the second edge portion and the first edgeportion in the rising portion thereof. Therefore, even when thethickness of the first organic buffer layer, which is an upper layer anda small size, is large and the angle of the first edge portion is large,the gas barrier layer gradually rises. In this way, it is possible tosufficiently increase the total thickness of the first and secondorganic buffer layers covering a region in which the plurality oflight-emitting elements are arranged, while slightly increasing the riseangle of the gas barrier layer. Thus, it is possible to prevent the gasbarrier layer from being cracked or peeled off, and to further improvethe sealing property of the light-emitting elements.

In the above-mentioned light-emitting device according to this aspect,preferably, an angle formed between an upper surface of the firstorganic buffer layer (or the second organic buffer layer) and an upperlayer of the substrate at the edge of the first organic buffer layer (orthe second organic buffer layer) is equal to or smaller than 20°.According to this structure, it is possible to sufficiently decrease therise angle of the gas barrier layer. Therefore, it is possible toprevent stress concentration on the gas barrier layer and thus toprevent the gas barrier layer from being cracked or peeled off.

According to another aspect of the invention, an electronic apparatusincludes the above-mentioned light-emitting device. In theabove-mentioned light-emitting device, the light-emitting elements arereliably sealed with the gas barrier layer that is prevented from beingcracked or peeled off. Therefore, according to the electronic apparatusaccording to this aspect, it is easy to maintain a good display qualityfor a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers refer to like elements.

FIG. 1 is a cross-sectional view illustrating an organic EL panelaccording to a first embodiment of the invention;

FIG. 2 is an enlarged cross-sectional view illustrating a portion A ofFIG. 1;

FIG. 3 is a cross-sectional view illustrating an organic EL panelaccording to a second embodiment of the invention;

FIG. 4 is an enlarged cross-sectional view illustrating a portion B ofFIG. 3;

FIG. 5 is a cross-sectional view illustrating an organic EL panelaccording to a third embodiment of the invention;

FIG. 6 is an enlarged cross-sectional view illustrating a portion C ofFIG. 5;

FIG. 7 is a cross-sectional view illustrating an organic EL panelaccording to a fourth embodiment of the invention;

FIG. 8 is an enlarged cross-sectional view illustrating a portion D ofFIG. 7;

FIG. 9 is a cross-sectional view illustrating an organic EL panelaccording to a fifth embodiment of the invention;

FIG. 10 is an enlarged cross-sectional view illustrating a portion E ofFIG. 9;

FIG. 11 is a cross-sectional view illustrating an organic EL panelaccording to a sixth embodiment of the invention;

FIG. 12 is an enlarged cross-sectional view illustrating a portion F ofFIG. 11;

FIG. 13 is a diagram illustrating the appearance of a personal computerhaving the organic EL panel according to any one of the embodiments ofthe invention applied thereto;

FIG. 14 is a diagram illustrating the appearance of a cellular phonehaving the organic EL panel according to any one of the embodiments ofthe invention applied thereto;

FIG. 15 is a longitudinal sectional view illustrating an example of animage printing apparatus using the organic EL panel according to any oneof the embodiments of the invention; and

FIG. 16 is a longitudinal sectional view illustrating another example ofthe image printing apparatus using the organic EL panel according to anyone of the embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be describedwith reference to the accompanying drawings. In the following drawings,a scale of each member is appropriately adjusted in order to have arecognizable size. Since cross sections are shown in FIGS. 1 to 12,hatching is omitted except some parts in the drawings. In the followingdescription, an ‘upper side’ and a ‘lower side’ are based on the planeof the drawing, and the ‘thickness’ of a layer means the length of thelayer in the vertical direction in the cross-sectional view.

First Embodiment

An organic EL panel (light-emitting device) according to a firstembodiment of the invention is a full color panel using a polymerorganic EL material, which will be described later. The organic EL panelhas an organic EL element emitting a red light component, an organic ELelement emitting a green light component, and an organic EL elementemitting a blue light component that are arranged side by side and iscapable of performing full color display. The organic EL panel is a topemission type in which light from the organic EL element is emitted fromthe opposite side of a main substrate.

Structure

FIG. 1 is a cross-sectional view of the organic EL panel. FIG. 2 is anenlarged cross-sectional view illustrating a portion A of the organic ELpanel. The organic EL panel includes a flat main substrate 10. The mainsubstrate 10 is formed of, for example, glass or plastic, and has aplurality of organic EL elements P1 formed on the upper surface thereof.The organic EL element P1 includes an organic light-emitting layer 16formed of a polymer organic EL material, which will be described later,and is supplied with a current at an emitting timing to cause theorganic light-emitting layer 16 (more specifically, a light-emittinglayer in the organic light-emitting layer 16) to emit light. The organicEL elements P1 are divided into three types according to the colors ofemission light components. These three types of organic EL elements P1are regularly arranged on the main substrate 10.

A plurality of TFTs (thin film transistors) 11 having a one-to-onecorrespondence to the plurality of organic EL elements P1 and variouswiring lines (only some of the wiring lines are shown in the drawings)are formed on the main substrate 10. The TFT 11 receives electric energyand control signals to drive the corresponding organic EL element P1.More specifically, the TFT 11 supplies electric energy to thecorresponding organic EL element P1. An inorganic insulating layer 12 isformed on the main substrate 10 so as to cover the plurality of TFTs 11.The inorganic insulating layer 12 insulates the plurality of TFTs 11from various wiring lines, and is formed of, for example, a siliconcompound.

A lyophilic bank layer (inorganic pixel partition wall insulating layer)13 is formed of, for example, silicon dioxide with a thickness of about50 to 200 nm on the inorganic insulating layer 12. A lyophobic banklayer (organic pixel partition wall insulating layer) 14 is formed of,for example, acrylic resin or polyimide with a thickness of about 1 to 3μm on the lyophilic layer 13. Concave portions are formed by theinorganic insulating layer 12, the lyophilic bank layer 13, and thelyophobic bank layer 14, and the organic EL element P1 occupies thebottom of each of the concave portions. Since a light-emitting deviceand an electronic apparatus using a single color does not needmulti-color coating, the lyophobic bank layer 14 may not be provided,and the organic light-emitting layer 16 may be formed by, for example, aspin coating method or a slit coating method so as to be laid across ananode 15 and the lyophilic bank layer 13.

The organic EL element P1 includes the anode 15, a common cathode layer17, and the organic light-emitting layer 16 interposed therebetween. Theanode 15 and the common cathode layer 17 are electrodes for injectingholes and electrons into the organic light-emitting layer 16, andgenerate an electric field by means of electric energy supplied. Theanode 15 is an electrode that is formed of, for example, ITO (Indium TinOxide) having a high hole-injecting property with a work function higherthan, for example, 5 eV on the inorganic insulating layer 12. The anode15 is connected to the corresponding TFT 11 through the wiring line. Thecommon cathode layer 17 is formed on the organic light-emitting layer 16and the lyophobic bank layer 14 and functions as a common electrodelying over the plurality of organic EL element P1. For example, thecommon cathode layer 17 includes an electron injection buffer layer formaking it easy to inject electrons into the organic light-emitting layer16 and a layer formed of a metallic material having low electricresistance, such as ITO or aluminum, on the electron injection bufferlayer. The electron injection buffer layer is formed of, for example,lithium fluoride, calcium metal, or magnesium-silver alloy.

The organic light-emitting layer 16 includes a light-emitting layer thatis excited by recombination of electrons and holes injected by theelectric field and emits light. Alternatively, the organiclight-emitting layer 16 may be formed in a multilayer structureincluding layers other than the light-emitting layer. In this case, itis preferable that the total thickness of all layers be smaller than 300nm in order to reduce the electrical resistance of the layers. Thelayers other than the light-emitting layer include a hole injectionlayer for making it easy to inject holes, a hole transfer layer formaking it easy to transfer the injected holes to the light-emittinglayer, an electron injection layer for making it easy to injectelectrons, and an electron transfer layer for making it easy to transferthe injected electrons to the light-emitting layer. These layerscontribute to the recombination.

The light-emitting layer is formed of a polymer organic EL material. Thepolymer organic EL material is a material having a relatively highmolecular weight among organic compounds that are excited by therecombination of electrons and holes and emit light. The polymer organicEL material forming the organic EL element P1 depends on the type (thecolor of emission light) of organic EL elements P1. A layer contributingto the recombination in the light-emitting layer is formed of a materialcorresponding to the material forming an adjacent layer. When thesematerials are diluted with a solvent and are applied in a pattern by,for example, an ink-jet method or other printing methods, the materialforming the organic light-emitting layer 16 is repelled from the surfaceof the lyophobic bank layer 14 to cause pixels to be colored indifferent colors. When multi-color coating is not needed, that is, asingle color is coated, the lyophobic bank layer 14 may not be provided,and the organic light-emitting layer 16 may be formed by, for example,the spin coating method or the slit coating method so as to be laid overthe lyophilic bank layer 13 and the anode 15, which also enables theseparation of pixels. The lyophilic bank layer 13 serves to stabilizethe thickness of the organic light-emitting layer 16 up to the edge ofthe anode 15 provided on the bottom of the concave portion, and theorganic light-emitting layer 16 is formed on the lyophilic bank layer13. The lyophilic bank layer 13 is formed of, for example, silicondioxide with a thickness of about 50 to 200 nm.

A cathode protecting layer 18 is formed on the inorganic insulatinglayer 12 and the common cathode layer 17 so as to cover the commoncathode layer 17. A first organic buffer layer 191 is formed on thecathode protecting layer 18 so as to overlap all the organic EL elementsP1 to planarize unevenness due to pixel partition walls. A secondorganic buffer layer 192 is formed on the first organic buffer layer 191so as to overlap all the organic EL elements P1. A gas barrier layer 20is formed on the cathode protecting layer 18, the first organic bufferlayer 191, and the second organic buffer layer 192 so as to completelycover the first organic buffer layer 191 and the second organic bufferlayer 192 including the edges thereof.

The gas barrier layer 20 contributes to improving the sealing of thefirst organic buffer layer 191, the second organic buffer layer 192, andthe plurality of organic EL elements P1, and adheres closely to thefirst organic buffer layer 191 and the second organic buffer layer 192.The gas barrier layer 20 is formed of a material having hightransmittance, gas barrier property, and water-resistance, such as asilicon compound including silicon oxynitride, silicon nitride, andSiNH. A thin film made of a high-quality inorganic compound is formed,as the gas barrier layer, at low temperature and high density by ahigh-density plasma deposition method, such as a CVD method, ionplating, or sputtering using ICP or ECR plasma or high-density plasmagenerated from a plasma gas. The thickness of the gas barrier layer 20depends on the sealing performance of the plurality of organic ELelements P1, the possibility of a crack occurring in the gas barrierlayer or the possibility of the gas barrier layer being peeled off, andmanufacturing costs. More specifically, the thickness of the gas barrierlayer 20 is in the range of 300 nm to 800 nm.

The first organic buffer layer 191 and the second organic buffer layer192 are provided to improve the flatness and adhesion of the gas barrierlayer 20 and to buffer stress occurring in the gas barrier layer 20. Theorganic buffer layers are formed as follows: an organic buffer layermaterial (liquid) having the following viscosity and composition isapplied in the uneven portions formed by the pixel partition walls tocontrol the thickness thereof by a screen printing method in a lowpressure atmosphere; the upper surface of the second organic bufferlayer is planarized by using a screen mesh and squeegee; and the organicbuffer layer material is hardened. A region of the main substrate 10overlapping the second organic buffer layer 192 is formed to have asmaller area than another region of the main substrate 10 overlappingthe first organic buffer layer 191 so that it is included in anotherregion.

The first organic buffer layer 191 preferably has a thickness of 3 μm to10 μm, and includes a first covering portion 191 a overlapping all theorganic EL elements P1, a first constant portion 191 b that has aconstant thickness and surrounds the first covering portion 191 a, and afirst edge portion 191 c that surrounds the first constant portion 191 band is tapered off toward the edge thereof. Since the first organicbuffer layer 191 is formed by applying a liquid material, an angle θ1formed between the upper surface of the first edge portion 191 c and theupper surface of the main substrate 10 at the edge of the first organicbuffer layer 191 corresponds to the thickness of the first constantportion 191 b. In this embodiment, the upper limit of the thickness ofthe first constant portion 191 b is determined such that the angle θ1 issmaller than 20°. Therefore, the upper surface of the first coveringpotion 191 a is planarized.

Meanwhile, the thickness of the second organic buffer layer 192 is inproportion to the height of the pixel partition wall, and is preferablyin the range of 3 μm to 20 μm. In addition, the second organic bufferlayer 192 includes a second covering portion 192 a overlapping all theorganic EL elements P1, a second constant portion 192 b that has aconstant thickness and surrounds the second covering portion 192 a, anda second edge portion 192 c that surrounds the second constant portion192 b and is tapered off toward the edge thereof. The second organicbuffer layer 192 is formed by applying a liquid material, and theapplication is performed to planarize the upper surface of the secondcovering portion 192 a. Therefore, the thickness of the second constantportion 192 b is larger than that of the first constant portion 191 b,and an angle θ2 formed between the upper surface and the lower surfaceof the second edge portion 192 c at the edge of the second organicbuffer layer 192 is larger than the angle θ1. In addition, thethicknesses of the first organic buffer layer 191 and the second organicbuffer layer 192 are determined, considering the coatability of the gasbarrier layer with respect to a foreign matter or the ratio of lightleaking from the side surface of an adhesive layer 21, which will bedescribed later, or the side surface of a surface protecting substrate22, which will be described later, without being incident on the uppersurface of the surface protecting substrate 22.

The cathode protecting layer 18 is provided to protect the commoncathode layer 17 and to improve the wettability and adhesion of thefirst organic buffer layer 191 before the organic buffer layer 191 ishardened. The cathode protecting layer 18 is formed of a siliconcompound, such as silicon oxynitride, having high light transmittance,adhesion, and water resistance. In particular, when the common cathodelayer 17 has a top emission structure, the thickness of the commoncathode layer 17 is made small in consideration of transparency, whichcauses a lot of pinholes to be generated. Since a small amount ofmoisture, which is adhered while a material forming the organic bufferlayer 19 is transported until the organic buffer layer 19 is formed, andthe material forming the organic buffer layer 19 infiltrated into theorganic light-emitting layer 16 before being hardened cause the organiclight-emitting layer 16 to be damaged, and the damaged portion of theorganic light-emitting layer 16 becomes a dark spot, the cathodeprotecting layer 18 serves to prevent the damage. Therefore, thethickness of the cathode protecting layer 18 is larger than 100 nm. Inaddition, on the upper surface of the common cathode layer 17,unevenness exists due to the step difference between the lyophobic banklayer 14 and the organic EL element P1, which causes stress toconcentrate on the cathode protecting layer 18. In order to preventdamage due to the stress concentration, the thickness of the cathodeprotecting layer 18 is set to 200 nm or less.

Furthermore, the adhesive layer 21 is formed on the main substrate 10 soas to cover the inorganic insulating layer 12, the cathode protectinglayer 18, and the gas barrier layer 20. The surface protecting substrate22 is fixed to the adhesion layer 21 so as to overlap the entire surfaceof the adhesion layer 21. The entire lower surface of the surfaceprotecting substrate 22 is adjacent to the adhesive layer 21. Theadhesive layer 21 is provided for adhesion between the surfaceprotecting substrate 22 and the main substrate 10 and is formed of aresin adhesive having high light transmittance. The resin adhesiveincludes, for example, epoxy resin, acrylic resin, urethane resin, andsilicon resin. The surface protecting substrate 22 is provided toimprove optical characteristics and to protect the gas barrier layer andis formed of glass or plastic having high light transmittance. Theplastic includes, for example, polyethyleneterephthalate, acrylic resin,polycarbonate, and polyolefin. In addition, the surface protectingsubstrate 22 may have the function of a color filter, a function ofblocking/absorbing ultraviolet rays, a function of preventing thereflection of external light, and a function of dissipating heat. Whenan optical function, such as a color filter, is not needed from theviewpoint of manufacturing costs, only the adhesive layer 21 isprovided, but the surface protecting substrate may not be provided.

Manufacturing Procedure

In order to manufacture the organic EL panel according to the presentembodiment, first, the TFTs 11, various wiring lines, and the inorganicinsulating layer 12 are formed on the main substrate 10. Then, areflective layer, which has a light-reflective property and is formedof, for example, an aluminum-copper alloy material, and transparent ITOare deposited on the inorganic insulating layer 12 by using a sputteringmethod, thereby forming the anodes 15 serving as a plurality of pixels.In this way, the anodes 15 are connected to the TFTs 11 for on/offcontrol. Then, the lyophilic bank layer 13 is formed on the inorganicinsulating layer 12 so as to surround the anodes 15. Subsequently, thelyophobic bank layer 14, which is formed of an organic compound, such aspolyimide or acrylic resin, is formed on the lyophilic bank layer 13.Then, a cleaning process, such as plasma cleaning, is performed toremove organic-based contamination from the main substrate 10 and toimprove the wettability of the ITO surface.

Thereafter, the organic light-emitting layer 16 is formed on the anodes15. In this process, when a material forming the organic light-emittinglayer 16 is coated, the material is flatly spread adjacent to the anode15 and the lyophilic bank layer 13. Thus, the organic light-emittinglayer 16 that is flat and has a constant thickness is formed. In aprocess of forming a light-emitting layer included in the organiclight-emitting layer 16, a polymer-based organic EL material used toform the organic light-emitting layer 16 that emits red light is coatedon the anode 15 which is to form the organic EL element P1 that emitsred light. The same process as above is performed for the organic ELelement P1 that emits green light and the organic EL element P1 thatemit blue light. A spin coating method or a slit coating method may beused as the coating method. When three kinds of coloring materials arecoated, it is preferable to perform pattern coating for each pixel byusing an inkjet printing method or a screen printing method, in order tocoating materials with a high degree of efficiency. When the organiclight-emitting layer 16 has a plurality of layers, the plurality oflayers are sequentially formed.

Then, an electrode common to the plurality of organic EL elements P1,that is, the common cathode layer 17 is formed. For example, a metallicmaterial or an alloy into which electrons can be easily injected, suchas lithium fluoride, calcium, or magnesium, is deposited by means of avacuum deposition method using a heating boat (crucible). Then, in orderto reduce the resistance of the common electrode, aluminum is depositedso as to avoid pixel units by means of the vacuum deposition method, ortransparent ITO is deposited in a low pressure atmosphere by means of ahigh-density plasma deposition method, such as an ECR (electroncyclotron resonance) plasma sputtering method, an ion plating method, oran opposite target sputtering method. Then, an oxygen plasma process isperformed, and then the cathode protecting layer 18, which is formed ofsilicon oxynitride, is formed so as to cover the common cathode layer 17by means of the high-density plasma deposition method, such as the ECRplasma sputtering method or the ion plating method. Here, the oxygenplasma process is performed to improve the adhesion between the commoncathode layer 17 and the cathode protecting layer 18.

Subsequently, an organic buffer layer material in a liquid state, whichhas a viscosity of 2000 mPa·s to 10000 mPa·s at the room temperature(25° C.), is printed on the cathode protecting layer 18 by using ascreen printing method in a low pressure atmosphere, and nitrogen gas isintroduced for the change to atmospheric pressure. Then, the cathodeprotecting layer 18 having the organic buffer layer material coatedthereon is carried into a curing chamber, in which the organic bufferlayer material corresponding to each substrate is heated at atemperature of 60 to 100° C. such that the organic buffer layer materialis completely cured, thereby forming the first organic buffer layer 191.The reason why the process of forming the first organic buffer layer 191is performed in the low pressure atmosphere is to remove moisture andbubbles generated during a coating process. That is, unlike in theprocess of forming the common cathode layer 17 or the cathode protectinglayer 18, while the organic buffer layer material is coated in arelatively low vacuum condition of 100 to 5000 Pa, the moisture isremoved until a dew point reaches −60° C. or less by introducingnitrogen. In addition, the reason why the organic buffer layer materialhaving a viscosity of 2000 mPa·s or more at the room temperature is usedis to avoid that the organic buffer layer material is infiltrated intothe common cathode layer 17 or the organic light-emitting layer 16through the cathode protecting layer 18.

An organic compound having high fluidity and not having a volatilecomponent, unlike a solvent, before being hardened can be used as a mainingredient of the organic buffer layer material (for example, more than70 weight %). In this embodiment, an epoxy monomer containing an epoxygroup and having a molecular weight of 3000 or less (molecular weight of3000 or less)/oligomer (molecular weight of 1000 to 3000) is used.Specifically, for example, any of the following materials orcombinations thereof can be used: bisphenol A type epoxy oligomer orbisphenol F type epoxy oligomer, phenol novolac type epoxy oligomer,3,4-epoxycyclohexenylmethyl-3′,4′-epoxycyclohexenecarboxylate, andε-caprolactone-modified3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexenecarboxylate.

A hardening agent reacting with epoxy monomer/oligomer is used as asub-ingredient of the organic buffer layer material. An agent capable offorming a hard film having high electrical insulating performance,solidity, and heat resistance is preferably used as the hardening agent.Alternatively, addition polymer having high transmittance and a smallamount of variation in hardness may be used as the hardening agent. Morespecifically, an acid-anhydride-based hardening agent, such as3-methyl-1,2,3,6-tetrahydrophthalic anhydride,methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride,1,2,4,5-benzenetetracarboxylic dianhydride,3,3′,4,4′-benzophenonetetracarboxylic dianhydride, or a polymer thereofis preferably used as the hardening agent. The first reason why theacid-anhydride-based hardening agent is preferable is that the hardeningof the acid-anhydride-based hardening agent is performed at atemperature of 60 to 100° C. and the hard film thereof becomes a polymerhaving an ester bonding having good adhesion to silicon oxynitride. Thesecond reason is that the hardening agent can be hardened at lowtemperature in a short time since when a material having a relativelyhigh molecular weight, such as aromatic amines, alcohols, or aminophenolis added thereto as a hardener for hastening a ring-opening of acidanhydride. The third region is that the hardening agent does not causedamage of each unit due to sharp hardening and shrinkage, as comparedwith photoinitiator of a cation emission type.

A water supplementing agent, such as a silane coupling agent or anisocyanate compound, and an additive for preventing shrinkage at thetime of hardening, such as minute particles, may be dispersed as othersub-ingredients of the organic buffer layer material to improve adhesionto the common cathode layer 17 or the first gas barrier layer 20. Theviscosity of the above-mentioned materials before being hardened ispreferably in the range of 1000 mPa·s to 10000 mPa·s at roomtemperature.

The viscosity of each of the main ingredients and the sub-ingredientsused in the present embodiment, before being cured, is preferably 1000mPa·s or more at room temperature. This is to reduce a possibility thatthe materials before being cured will be infiltrated into the organiclight-emitting layer 16. In addition, the viscosity of these materialsmay be determined in consideration of whether the organic buffer layercan be formed with required pattern accuracy, whether the organic bufferlayer 191 can be formed with a desired thickness, and whether bubblesare not generated in the formed organic buffer layer.

Next, the second organic buffer layer 192 is formed by printing the sameorganic buffer layer material as described above on the first organicbuffer layer 191 by a screen printing method in a low pressureatmosphere, applying pressure thereto in a nitrogen gas atmosphere, andheating the material at a temperature of 60 to 100° C. to completelyharden the material. The organic buffer layer material printed when thesecond organic buffer layer 192 is formed comes into contact with thefirst organic buffer layer 191, not the cathode protecting layer 18.Therefore, when the same material as that forming the first organicbuffer layer 191, having relatively high wettability, is used, it isdifficult to satisfy θ1<θ2. Therefore, in this embodiment, the secondorganic buffer layer 192 is formed of a material that slightly differsfrom the organic buffer layer material used for forming the firstorganic buffer layer 191 in at least one of viscosity and composition.

Then, an oxygen plasma process is performed in a low pressure atmosphereagain to form the gas barrier layer 20 so as to completely cover thefirst organic buffer layer 191 and the second organic buffer layer 192including their edges, by using a high-density plasma deposition method,such as an ECR sputtering method or an ion plating method. The oxygenplasma process is performed to improve adhesion between the secondorganic buffer layer 192 and the gas barrier layer 20. Subsequently, aresin adhesive having high transmittance is applied so as to cover theinorganic insulating layer 12, the cathode protecting layer 18, and thegas barrier layer 20, and the entire lower surface of the surfaceprotecting substrate 22 is brought into contact with the resin adhesive.Then, the resin adhesive is hardened to form the adhesive layer 21.Alternatively, a liquid adhesive may be used instead of the resinadhesive, or the second gas barrier layer 12 and the surface protectingsubstrate 22 may be bonded to each other by interposing a sheet-shapedadhesive between the second gas barrier layer 12 and the surfaceprotecting substrate 22 and applying pressure thereto.

Effects

In the organic EL panel according to this embodiment, since the organicbuffer layer has a two-layer structure, the thickness of each of theorganic buffer layers is smaller than that of the organic buffer layerhaving a single-layer structure. Therefore, the angle of the edge ofeach of the organic buffer layers is smaller than that of the organicbuffer layer having a single-layer structure. More specifically, theangle of the first edge portion 191 c of the first organic buffer layer191 is smaller than 20°. In addition, a region of the main substrate 10overlapping the second organic buffer layer 192 is included in a regionof the main substrate 10 overlapping the first organic buffer layer 191,and the second constant portion 192 b and the second edge portion 192 coverlap the first constant portion 191 b. Therefore, the angle of arising portion of the gas barrier layer 20 slightly increases, whichmakes it difficult for the gas barrier layer 20 to be split or peeledoff. Thus, according to the organic EL panel of this embodiment, sincethe gas barrier layer 20 is hardly split or peeled off, it is possibleto reliably seal a plurality of organic EL elements P1 with the gasbarrier layer 20.

Further, according to the organic EL panel, the thickness of the secondorganic buffer layer 192, which is an upper layer, is larger than thatof the first organic buffer layer 191, which is a lower layer, but thesize of the second organic buffer layer 192 is smaller than that of thefirst organic buffer layer 191. Therefore, in order to improve thesealing property of the plurality of organic EL elements P1, even whenthe total thickness of the first organic buffer layer 191 and the secondorganic buffer layer 192 is sufficiently large, the rise angle of thegas barrier layer 20 is equal to that of the first edge portion 191 c ofthe first organic buffer layer 191 having a smaller thickness than thesecond organic buffer layer 192. In addition, since the second constantportion 192 b and the second edge portion 192 c overlap the firstconstant portion 191 b, the gas barrier layer 20 rises along the firstedge portion 191 c and the second edge portion at the rising portion.Therefore, even when the thickness of the second organic buffer layer192, which is an upper layer having a small size, is large and the angleof the second edge portion 192 c is inclined at a large angle, the gasbarrier layer 20 gradually rises. In this way, it is possible tosufficiently increase the total thickness of the first organic bufferlayer 191 and the second organic buffer layer 191 overlapping theplurality of organic EL elements P1 while gradually raising the gasbarrier layer 20.

For example, a cap-shaped sealing substrate is used to seal the organicEL elements. Meanwhile, an increase in the size of the organic EL paneland a reduction in the thickness and weight thereof have been demanded.In order to meet the demands, when the cap-shaped sealing substrate isused, the edges of the sealing substrate and the main substrate aresealed by an adhesive, which makes it difficult to make the organic ELpanel have sufficient strength against external stress. In contrast, inthe organic EL panel according to this embodiment, a so-called thinsealing film comes into contact with the plurality of organic ELelements P1 with a large contact area to seal the organic EL elementsP1, which makes it possible to remarkably improve the strength of theorganic EL panel, to prevent the gas barrier layer from being cracked orpeeled off, and to improve the sealing property of the plurality oforganic EL elements P1. Therefore, the organic EL panel according tothis embodiment can meets the demands for an increase in the size of theorganic EL panel and a reduction in the thickness and weight thereof.When the size of the organic EL panel becomes large, the number of TFTsand wiring lines provided between the organic EL elements and the mainsubstrate increases. Therefore, in a bottom emission type in which lightfrom an organic light-emitting layer is emitted from the main substrate,the aperture ratio of pixels may be reduced and thus luminous efficiencymay be lowered. However, since the organic EL panel is a top emissiontype, the above-mentioned problems do not arise.

In order to prevent the adhesion of a foreign material, such as dust, orwater, it is preferable that the organic EL panel be manufactured undera high vacuum lower than 1 Pa. However, since the organic buffer layermaterial is in a liquid state, it is difficult to form the organicbuffer layer under high vacuum. Therefore, in this embodiment, theorganic buffer layer is formed by a screen printing method in a lowpressure atmosphere in the range of 100 to 5000 Pa. This contributes tothe removal of pinholes of the gas barrier layer by removing bubblesgenerated at the time of coating and covering the foreign material. Inaddition, the gas barrier layer is formed by a high-density plasmadeposition method under a high vacuum of 0.1 to 10 Pa at lowtemperature. Therefore, when the gas barrier layer is formed, theplurality of organic EL elements are not damaged. As can be apparentlyseen from the above-mentioned manufacturing procedure, a process ofsealing the organic EL panel is little affected by minute foreignmaterials existing even in a clean room. This is very advantageous,considering the fact that it is difficult to perform a cleaning processuntil the sealing process is finished once the formation of the organiclight-emitting layer starts.

Second Embodiment

An organic EL panel according to a second embodiment of the invention issimilar to the organic EL panel according the first embodiment exceptfor the structure of an organic buffer layer.

FIG. 3 is a cross-sectional view of the organic EL panel. FIG. 4 is anenlarged cross-sectional view illustrating a portion B of the organic ELpanel. In the organic EL panel, a first organic buffer layer 193 isformed on a cathode protecting layer 18 so as to overlap a plurality ofEL elements P1. A second organic buffer layer 194 is formed on the firstorganic buffer layer 193 so as to cover the first organic buffer layer193. A gas barrier layer 20 is formed on the cathode protecting layer18, the first organic buffer layer 193, and the second organic bufferlayer 194 so as to cover both the organic buffer layers.

The first organic buffer layer 193 and the second organic buffer layer194 are provided to improve the flatness and adhesion of the gas barrierlayer 20 and to buffer stress occurring in the gas barrier layer 20. Theorganic buffer layers are formed by applying the above-mentioned organicbuffer layer material in a low pressure atmosphere and hardening thematerial. Then, the two organic buffer layers are bonded to each other.A region of the main substrate 10 overlapping the first organic bufferlayer 193 is included in another region of the main substrate 10overlapping the second organic buffer layer 194.

The first organic buffer layer 193 includes a first covering portion 193a overlapping all the organic EL elements P1, a first constant portion193 b that has a constant thickness and surrounds the first coveringportion 193 a, and a first edge portion 193 c that surrounds the firstconstant portion 193 b and is tapered off toward the edge thereof. Sincethe first organic buffer layer 193 is formed by applying a liquidmaterial, an angle θ3 formed between the upper surface of the first edgeportion 193 c and the upper surface of the main substrate 10 at the edgeof the first organic buffer layer 193 corresponds to the thickness ofthe first constant portion 193 b.

Meanwhile, the second organic buffer layer 194 includes a secondcovering portion 194 a overlapping all the organic EL elements P1, asecond constant portion 194 b that has a constant thickness andsurrounds the second covering portion 194 a, and a second edge portion194 c that surrounds the second constant portion 194 b and is taperedoff toward the edge thereof. The second organic buffer layer 194 isformed by applying a liquid material, and the application is performedto planarize the upper surface of the second covering portion 194 a.

In this embodiment, the upper limit of the thickness of the secondconstant portion 194 b is determined such that a rise angle θ4 of thesecond edge portion 194 c is smaller than 20° at the edge of the secondorganic buffer layer 194. When the second organic buffer layer 194 isformed to satisfy the condition, the thickness of the first constantportion 193 b, that is, the rise angle θ3 of the first organic bufferlayer 193 is determined such that the upper surface of the secondcovered potion 194 a is planarized. In this embodiment, θ3 isapproximately equal to 04. In addition, the thickness of the firstorganic buffer layer 193 is determined, considering the height of pixelpartition walls or the ratio of light leaking from the side surface ofthe surface protecting substrate 22 or the side surface of an adhesivelayer, which will be described later, such that light effectively passesthrough the upper surface of the surface protecting substrate 22 having,for example, the function of a color filter.

In the organic EL panel according to this embodiment, the organic bufferlayer has a two-layer structure, and a region of the main substrate 10overlapping the first organic buffer layer 193, which is a lower layer,is included in a region of the main substrate 10 overlapping the secondorganic buffer layer 194, which is an upper layer. In addition, thethickness of the first organic buffer layer 193 is larger than that ofthe second organic buffer layer 194. Further, the first constant portion193 b and the first edge portion 193 c overlap the second constantportion 194 b. Therefore, the organic EL panel according to the secondembodiment can obtain the same effects as the organic EL panel accordingto the first embodiment.

In the organic EL panels according to the first and second embodiments,it is difficult for the gas barrier layer to be split or peeled off,which makes it possible for light to be continuously emitted withuniform brightness for a long time. Experiments are made to prove theabove. According to the experiments, the organic EL panels according tothe first and second embodiments and other organic EL panels arecontinuously exposed at a temperature of 60° C. and a relative humidity(RH) of 90% for 600 hours, and the luminous state after the exposure isexamined. The organic EL panels used for the experiments each have pixelpartition walls having an average step difference of 3 μm, organicbuffer layers formed of epoxy resin, and a gas barrier layer (having athickness of 500 nm) formed of silicon oxynitride.

As the results of the experiments, in the organic EL panel having onlyone organic buffer layer that includes a constant portion having athickness of 20 μm (an angle formed between the upper surface of theorganic buffer layer and the upper surface of the main substrate at theedge of the organic buffer layer is in the range of 20 to 25°), some ofthe plurality of organic EL elements arranged in a peripheral portion(the periphery of a tapered portion of the organic buffer layer) havebad luminous efficiency. In the organic EL panel which has two organicbuffer layers, each including a constant portion having a thickness of10 μm, and in which a region of the main substrate overlapping a lowergas barrier layer completely corresponds to a region of the mainsubstrate overlapping an upper gas barrier layer (an angle formedbetween the upper surface of the organic buffer layer and the uppersurface of the main substrate at the edge of the organic buffer layer isin the range of 25 to 30°), some of the plurality of organic EL elementsarranged in a peripheral portion have bad luminous efficiency. Thereason why the organic EL elements arranged in the peripheral portionhave bad luminous efficiency in both the organic EL panels is that thegas barrier layer positioned in the vicinity of a tapered portion of theorganic buffer layer is split or peeled off, which causes water to beinfiltrated thereinto.

In contrast, in the organic EL panel according to the second embodimentwhich has two organic buffer layers, each having a thickness of 10 μm,and in which a region of the main substrate overlapping one organicbuffer layer close to the main substrate is included in another regionof the main substrate overlapping the other organic buffer layer farfrom the main substrate (an angle formed between the upper surface ofthe organic buffer layer having a larger size and the upper surface ofthe main substrate at the edge of the organic buffer layer is in therange of 10 to 15°), all the organic EL elements have good luminousefficiency.

In the organic EL panel according to the first embodiment which has twoorganic buffer layers, that is, a first organic buffer layer having athickness of 5 μm and a second organic buffer layer having a thicknessof 10 μm and in which a region of the main substrate overlapping thesecond organic buffer layer is included in another region of the mainsubstrate overlapping the first organic buffer layer (an angle formedbetween the upper surface of the first organic buffer layer and theupper surface of the main substrate at the edge of the first organicbuffer layer is in the range of 5 to 10°), all the organic EL elementshave good luminous efficiency. In addition, in the organic EL panelincluding the second organic buffer layer (having a small size) having athickness of 20 μm (an angle formed between the upper surface of thefirst organic buffer layer and the upper surface of the main substrateat the edge of the first organic buffer layer is in the range of 5 to10°), all the organic EL elements also have good luminous efficiency.

Third Embodiment

The structure of an organic buffer layer of an organic EL panelaccording to a third embodiment of the invention is the same as that ofthe organic buffer layer of the organic EL panel according to the secondembodiment. However, the organic EL panel according to the thirdembodiment is a full color panel using a low-molecular-weight-basedorganic EL material, which will be described later, and can perform fullcolor display using organic EL elements emitting white light and colorfilters.

Structure

FIG. 5 is a cross-sectional view illustrating the organic EL panel, andFIG. 6 is an enlarged cross-sectional view illustrating a portion C ofthe organic EL panel. The organic EL panel includes a flat mainsubstrate 30. The main substrate 30 is formed of glass or plastic, and aplurality of organic EL elements P2 are formed on the main substrate 30.The organic EL element P2 is an element that emits white light, has anorganic light-emitting layer 37 formed of a low-molecular-weight-basedorganic EL material, which will be described later, and is supplied withelectric energy to cause the organic light-emitting layer 37(specifically, a light-emitting layer within the organic light-emittinglayer 37) to emit light.

Further, a plurality of TFTs 31, which correspond to the plurality oforganic EL elements P2, and various wiring lines (not shown) are formedon the main substrate 30. Similar to the TFTs 11 in the secondembodiment, the TFTs 31 drive the corresponding organic EL elements P2.In addition, an inorganic insulating layer 32 is formed on the mainsubstrate 30 so as to cover the plurality of TFTs 31. The inorganicinsulating layer 32 is provided to insulate the plurality of TFTs 31from various wiring lines and is formed of, for example, siliconnitride.

On a planarizing layer 33 removing a step difference caused by thewiring lines or the TFTs, a pixel partition wall insulation layer 36that goes up from concave portions of the planarizing layer 33 is formedof an organic compound, such as polyimide or acrylic resin. The upperend of the pixel partition wall insulation layer 36 is positioned to behigher than convex portions of the planarizing layer 33, and theplanarizing layer 33 and the pixel partition wall insulation layer 36define the concave portions. A metal reflective layer 34 for reflectinglight emitted from the organic EL element P2 through the anode 35 isformed in the planarizing layer 33, and the metal reflective layer 34 isformed of a reflective metallic material. An inorganic insulating layerfor preventing corrosion is provided on the metal reflective layer 34below the bottom of the concave portion, and the anode 35 formed of ITOhaving a high work function is formed thereon.

The organic EL elements P2 each have the anode 35 and a common cathodelayer 38 with the organic light-emitting layer 37 interposedtherebetween. The anode 35 and the common cathode layer 38 serve aselectrodes for injecting holes and electrons into the organiclight-emitting layer 37. The anode 35 is a thin transparent electrodethat is formed on the planarizing layer 33 and is formed of, forexample, a metallic material, such as aluminum, or ITO. The anode 35 isconnected to the corresponding TFT 31 through a gap between theplanarizing layer 33 and the pixel partition wall insulation layer 36.The common cathode layer 38 is formed on the organic light-emittinglayer 37 and the pixel partition wall insulation layer 36 and serves asa common electrode with respect to the plurality of organic EL elementsP2. For example, the common cathode layer 38 has an electron injectionbuffer layer, which facilitates electrons to be injected into theorganic light-emitting layer 37, and a low-resistance layer, such as atransparent ITO layer formed on the electron injection layer or analuminum layer that is formed on a non-pixel region. The electroninjection buffer layer is formed of, for example, lithium fluoride ormagnesium-silver alloy.

The organic light-emitting layer 37 corresponds to the organiclight-emitting layer 16 in the second embodiment. The organiclight-emitting layer 37 according to the third embodiment differs fromthe organic light-emitting layer 16 according to the second embodimentin that the organic light-emitting layer 37 is formed continuously onthe anode 35 and the pixel partition wall insulation layer 36 and isformed of a low-molecular-weight-based organic EL material. Thelow-molecular-weight-based organic EL material is an organic compoundhaving a relatively low molecular weight, among organic compounds thatemit light by excitation due to the recombination of holes andelectrons. Examples of the low-molecular-weight-based organic ELmaterial include, for example, a material obtained by dopinganthracene-based impurities into styrylamine-base host, and a materialobtained by doping rubrene-based impurities into styrylamine-base host.When the organic light-emitting layer 37 includes an additional layercontributing to the recombination in the light-emitting layer, amaterial forming the additional layer is determined according to amaterial forming a layer adjacent to the additional layer. For example,the hole injection layer is formed of triallylamine (ATP) polymer, andthe hole transport layer is formed of, for example, a triphenyl diamine(TPD) based compound. In addition, the electron injection layer isformed of, for example, an aluminum quinolinol complex.

Furthermore, a cathode protecting layer 39 is formed on the inorganicinsulating layer 32 and the common cathode layer 38 so as to cover thecommon cathode layer 38 and the planarizing layer 33. In addition, afirst organic buffer layer 195 is formed on the cathode protecting layer39 so as to completely cover the plurality of organic EL elements P2,the pixel partition wall insulation layer 36, and the planarizing layer33. In addition, a second organic buffer layer 196 is formed on thecathode protecting layer 39 and the first organic buffer layer 195 so asto cover the first organic buffer layer 195. A gas barrier layer 20 isformed on the cathode protecting layer 39 and the second organic bufferlayer 196 so as to cover the second organic buffer layer 196.

The cathode protecting layer 39, the first organic buffer layer 195, andthe second organic buffer layer 196 correspond to the cathode protectinglayer 18, the first organic buffer layer 193, and the second organicbuffer layer 194 of the second embodiment. Therefore, the first organicbuffer layer 195 includes a first covering portion 195 a overlapping allthe organic EL elements P2, a first constant portion 195 b that has aconstant thickness and surrounds the first covering portion 195 a, and afirst edge portion 195 c that surrounds the first constant portion 195 band is tapered off toward the edge thereof. Meanwhile, the secondorganic buffer layer 196 includes a second covering portion 196 aoverlapping all the organic EL elements P2, a second constant portion196 b that has a constant thickness and surrounds the second coveringportion 196 a, and a second edge portion 196 c that surrounds the secondconstant portion 196 b and is tapered off toward the edge thereof.

In this embodiment, the upper limit of the thickness of the secondconstant portion 196 b is determined such that a rise angle θ6 of thesecond edge portion 196 c is smaller than 20° at the edge of the secondorganic buffer layer 196. When the second organic buffer layer 196 isformed to satisfy the condition, the thickness of the first constantportion 195 b, that is, a rise angle θ5 of the first organic bufferlayer 195 is determined such that the upper surface of the secondcovered potion 196 a is planarized. In this embodiment, θ5 isapproximately equal to θ6. In addition, the thickness of the firstorganic buffer layer 195 is determined, considering coatability for astep difference between pixel partition walls or the ratio of lightleaking from the side surface of an adhesive layer 21, which will bedescribed later, without reaching the lower surface of the color filtersubstrate 42.

Furthermore, an adhesive layer 21 is formed on the main substrate 30 soas to cover the inorganic insulating layer 32, the cathode protectinglayer 39, and the gas barrier layer 20. In addition, a color filtersubstrate 42 is fixed to the adhesive layer 21 so as to completelyoverlap the adhesive layer 21. The entire lower surface of the colorfilter substrate 42 is adjacent to the adhesive layer 21. The colorfilter substrate 42 is provided to extract red, green, and blue lightcomponents from light components emitted from the organic EL elementsP2, and includes a black matrix layer 43 having low light transmittanceand filter layers 44 that cover openings formed in the black matrixlayer 43. The black matrix layer 43 has a plurality of openings. Inaddition, three types of filter layers 44, that is, a filter layer fortransmitting only red light, a filter layer for transmitting only greenlight, and a filter layer for transmitting only blue light, areprovided. Each of the filter layers 44 overlaps the organic EL elementsP2. The red, green, and blue light components of the light componentsemitted from the organic EL elements P2 overlapping the filter layers 44are transmitted through the corresponding filter layers 46,respectively. Furthermore, the color filter substrate 42 serves toprotect the gas barrier layer, and portions other than the black matrixlayer 43 and the filter layers 44 are formed of glass or plastic havinghigh light transmittance. Examples of the plastic includepolyethyleneterephthalate, acrylic resin, polycarbonate, and polyolefin.In addition, the color filter substrate 42 may have a function ofblocking/absorbing ultraviolet rays, a function of preventing reflectionof external light, or a function of heat dissipation.

Manufacturing Procedure

In order to manufacture the organic EL panel according to the presentembodiment, first, the TFTs 31, various wiring lines, and the inorganicinsulating layer 32 are formed on the main substrate 30. Then, theplanarizing layer 33 and the metal reflective layer 34 are formed on theinorganic insulating layer 32. Then, in order to prevent corrosion ofthe metal reflective layer 34, the surface and a peripheral portion ofthe metal reflective layer 34 are coated with an inorganic insulatinglayer, and then a plurality of anodes 35 are formed. Thus, the TFTs 31and the anodes 35 are connected to each other in a one-to-one manner. Asa method of forming the anodes 35, it is possible to use one of theknown methods suitable for a material forming the anodes 35. Then, thepixel partition wall insulation layer 36 is formed on parts of theanodes 35 and the planarizing layer 33 by coating and patterning, forexample, polyimide. Then, a cleaning process, such as plasma cleaning,is performed to remove organic-based contamination from the mainsubstrate 30 or to increase the work function.

Thereafter, the organic light-emitting layer 37 common to the pluralityof organic EL elements P2 is formed on the exposed anodes 35. In thisprocess, a light-emitting layer is formed of alow-molecular-weight-based organic EL material. The process of formingthe organic light-emitting layer 37 is performed using a vacuumdeposition method using a heating boat. The vacuum deposition method canalso be applied to a case in which the organic light-emitting layer 37includes only a light-emitting layer or a case in which the organiclight-emitting layer 37 includes a plurality of layers. When the organiclight-emitting layer 37 includes the plurality of layers, the pluralityof layers are sequentially formed.

Then, an electrode common to the plurality of organic EL elements P2,that is, the common cathode layer 38 is formed. Subsequently, an oxygenplasma process is performed, and then the cathode protecting layer 39 isformed so as to cover the common cathode layer 38. Then, the firstorganic buffer layer 195 is formed on the cathode protecting layer 39 byusing a screen printing method in a low pressure atmosphere, and thesecond organic buffer layer 196 is formed. Successively, an oxygenplasma process is performed to form the gas barrier layer 20 so as tocover the second organic buffer layer 196.

Subsequently, a resin adhesive having high light transmittance is coatedso as to cover the inorganic insulating layer 32, the cathode protectinglayer 39, and the gas barrier layer 20. Then, the entire lower surfaceof the color filter substrate 42 comes in contact with the resinadhesive, and the resin adhesive is cured, thereby forming the adhesionlayer 21. This curing is performed at locations at which a plurality offilters 44 of the color filter substrate 42 overlap the correspondingplurality of organic EL elements P2. In addition, a variation of theadhesion of the surface protecting substrate 22 in the first embodimentcan also be applied to a variation of the adhesion of the color filtersubstrate 42.

Effects

In the organic EL device according to this embodiment, the organicbuffer layer has a two-layer structure, and a region of the mainsubstrate 30 overlapping the first organic buffer layer 195, which is alower layer and a smaller size, is included in a region of the mainsubstrate 30 overlapping the second organic buffer layer 196, which isan upper layer and has a larger area. In addition, the thickness of thefirst organic buffer layer 195 is larger than that of the second organicbuffer layer 196. Further, the first constant portion 195 b and thefirst edge portion 195 c overlap the second constant portion 196 b. Inthis way, the organic EL panel according to the third embodiment canhave the same effects as the organic EL panel according to the secondembodiment.

Fourth Embodiment

FIG. 7 is a cross-sectional view illustrating an organic EL panelaccording to a fourth embodiment of the invention. FIG. 8 is an enlargedcross-sectional view illustrating a portion D of the organic EL panel.As can be apparently seen from FIGS. 7 and 8, the organic EL panelaccording to the fourth embodiment is similar to the organic EL panelaccording to the first embodiment except for the structure of a gasbarrier layer.

In the organic EL panel according to this embodiment, the gas barrierlayer is divided into a first gas barrier layer 201 and a second gasbarrier layer 202. The first gas barrier layer 201 is formed on thecathode protecting layer 18, the first organic buffer layer 191, and thesecond organic buffer layer 192 such that it adheres closely to thefirst organic buffer layer 191 and the second organic buffer layer 192to cover the first and second organic buffer layers 191 and 192. Thesecond gas barrier layer 202 is formed on the first gas barrier layer201 such that it covers a plurality of organic EL elements P1 and theedge of the first organic buffer layer 191 is exposed. The two gasbarrier layers are formed of the same material as the gas barrier layer20 according to the first embodiment, and are closely adhered to eachother.

The first gas barrier layer 201 contributes to improving the sealing ofthe first organic buffer layer 191, the second organic buffer layer 192,and the plurality of organic EL elements P1. The thickness of the firstgas barrier layer 201 is in the range of 200 nm to 400 nm. The lowerlimit of the range is determined so as to sufficiently seal the sidesurfaces of the organic buffer layers and the peripheries thereof. Thesecond gas barrier layer 202 contributes to improving the sealing of theplurality of organic EL elements P1. The thickness of the second gasbarrier layer 202 is in the range of 200 nm to 800 nm. In thisembodiment, the thicknesses of the two gas barrier layers are restrictedsuch that the sum of the thickness of the first gas barrier layer 201and the thickness of the second gas barrier layer 202, that is, thetotal thickness of the two gas barrier layers is smaller than 1000 nm.The restriction of thickness is determined considering the degree of thesealing of the plurality of organic EL elements P1, the possibility ofthe gas barrier layer being cracked or peeled off, and manufacturingcosts.

The organic EL panel according to the fourth embodiment can obtain thesame effects as the organic EL panel according to the first embodiment.It is necessary to increase the thickness of the gas barrier layer inorder to improve the sealing property. However, when the gas barrierlayer has a constant thickness over the entire range, stressconcentrates on a non-flat portion of the gas barrier layer. Incontrast, according to this embodiment, since the gas barrier layerincludes the first gas barrier layer 201 and the second gas barrierlayer 202, it is possible to sufficiently increase the total thicknessof the gas barrier layers overlapping all the organic EL elements P1 andto decrease the thickness of the gas barrier layers at the edge of thefirst organic buffer layer 191 where the gas barrier layers rise. Thus,it is possible to improve the sealing property of the plurality oforganic EL elements P1 and to prevent the gas barrier layer from beingcracked or peeled off.

Fifth Embodiment

FIG. 9 is a cross-sectional view illustrating an organic EL panelaccording to a fifth embodiment of the invention. FIG. 10 is an enlargedcross-sectional view illustrating a portion E of the organic EL panel.As can be apparently seen from FIGS. 9 and 10, the organic EL panelaccording to the fifth embodiment is similar to the organic EL panelaccording to the second embodiment except for the structure of a gasbarrier layer. The organic EL panel according to this embodimentincludes a first gas barrier layer 203 and a second gas barrier layer204 corresponding to the first gas barrier layer 201 and the second gasbarrier layer 202 according to the fourth embodiment, respectively.

The organic EL panel according to the fifth embodiment can obtain thesame effects as the organic EL panel according to the second embodiment.The first gas barrier layer 203 and the second gas barrier layer 204,serving as the gas barrier layer, make it possible to improve thesealing property of a plurality of organic EL elements P1 and to preventthe gas barrier layer from being cracked or peeled off.

Sixth Embodiment

FIG. 11 is a cross-sectional view illustrating an organic EL panelaccording to a sixth embodiment of the invention. FIG. 12 is an enlargedcross-sectional view illustrating a portion F of the organic EL panel.As can be apparently seen from FIGS. 11 and 12, the organic EL panelaccording to the sixth embodiment is similar to the organic EL panelaccording to the third embodiment except for the structure of a gasbarrier layer. The organic EL panel according to this embodimentincludes a first gas barrier layer 205 and a second gas barrier layer206 corresponding to the first gas barrier layer 203 and the second gasbarrier layer 204 according to the fifth embodiment, respectively.

The organic EL panel according to the sixth embodiment can obtain thesame effects as the organic EL panel according to the third embodiment.The first gas barrier layer 205 and the second gas barrier layer 206,serving as the gas barrier layer, make it possible to improve thesealing property of a plurality of organic EL elements P1 and to preventthe gas barrier layer from being cracked or peeled off.

Modifications

According to a modification of the above-described embodiments, threeorganic buffer layers may be provided. However, in these organic bufferlayers, a region of the main substrate overlapping one organic bufferlayer should not completely overlap a region of the main substrateoverlapping another organic buffer layer. This structure is similarlyapplied to the gas barrier layer. As a modification of the fourth tosixth embodiments, the second barrier layer far from the main substratemay cover the first barrier layer close to the main substrate.

According to another modification of the above-described embodiments, apanel emitting monochromatic light may be used, or a full color panelhaving a color conversion layer may be used. Alternatively, abottom-emission-type panel may be used. In this case, only the layersbelow the light-emitting layer need to have high transmittance.Therefore, when the common cathode layer is arranged above thelight-emitting layer, the common cathode layer formed of a metallicmaterial having low resistance, such as aluminum, may be formed with alarge thickness on the entire surface of the light-emitting layer.

Electronic Apparatus

The above-mentioned organic EL panel can be applied to variouselectronic apparatuses. In the invention, the organic EL panel isapplied to an image display apparatus and an image printing apparatus.

Image Display Apparatus

An image display apparatus having the organic EL panel includes wiringlines for supplying electric energy and controls signals to the organicEL panel and a circuit for generating control signals allowing anoptical image to be formed on the organic EL panel on the basis of imagedata supplied from an external device. Various types of image displayapparatuses can be used, but in the invention, two types of imagedisplay apparatuses are exemplified.

FIG. 13 shows the structure of a personal computer using theabove-mentioned organic EL panel as a display unit 31. A personalcomputer 30 includes the display unit 31, serving as a display device,and a main body 32. The main body 32 is provided with a power switch 33and a keyboard 34. Since the personal computer 30 uses theabove-mentioned organic EL panel as the display unit 31, it is possibleto meet demands for an increase in the size of the display unit 31 and areduction in the thickness and weight of the display device 31. Inaddition, since the quality of light emitted from the organic EL panelis hardly deteriorated, it is easy to keep display quality for a longtime.

FIG. 14 shows the structure of a cellular phone using theabove-mentioned organic EL panel as a display unit 41. A cellular phone40 includes a plurality of operating buttons 42, a plurality of scrollbuttons 43, and the display unit 41 serving as a display device. Thescroll button 43 is operated to scroll a screen displayed on the displayunit 41. Since the cellular phone 40 uses the above-mentioned organic ELpanel as the display unit 41, it is possible to meet demands for areduction in the thickness and weight of the display device 41. Inaddition, since the quality of light emitted from the organic EL panelis hardly deteriorated, it is easy to keep display quality for a longtime.

Image Printing Apparatus

Next, an image printing apparatus using the above-mentioned organic ELpanel will be described. This type of image printing apparatus includesa printer, a printing unit of a copy machine, and a printing unit of afacsimile. The above-mentioned organic EL panel can be applied tovarious types of image printing apparatuses. However, in the invention,two types of electrophotographic full color image printing apparatusesare used as examples of the image printing apparatus.

FIG. 15 is a longitudinal sectional view showing an example of an imageprinting apparatus using the above-described organic EL panels asline-type exposure heads. The image printing apparatus is a tandem-typefull-color image printing apparatus using a belt intermediate transfermethod. In the image printing apparatus, four exposure heads 10K, 10C,10M, and 10Y having the same configuration are arranged at exposurepositions of four corresponding photoconductor drums (image carriers)110K, 110C, 110M, and 110Y having the same configuration.

As shown in FIG. 15, the image printing apparatus is provided with adriving roller 121 and a driven roller 122, and an endless intermediatetransfer belt 120 is wound around these rollers 121 and 122 so as torotate around the rollers 121 and 122 in a direction represented byarrow. Although not shown in FIG. 15, the image printing apparatus maybe provided with a tension applying member, such as a tension roller,that applies tension to the intermediate transfer belt 120.

The four photoconductor drums 110K, 110C, 110M, and 110Y each having aphotosensitive layer on its outer peripheral surface are arranged atpredetermined intervals from each other around the intermediate transferbelt 120. The suffixes K, C, M, and Y mean black, cyan, magenta, andyellow used for forming corresponding toner images, respectively. Thisis similarly applied to other members. The photoconductor drums 110K,110C, 110M, and 110Y are driven to rotate in synchronization with thedriving of the intermediate transfer belt 120.

A corona charging device 111 (K, C, M, and Y), the exposure head 10 (K,C, M, and Y), and a developing device 114 (K, C, M, and Y) are arrangedaround each photoconductor drum 110 (K, C, M, and Y). The coronacharging device 111 (K, C, M, and Y) uniformly charges the outerperipheral surface of the corresponding photoconductor drum 110 (K, C,M, and Y). The exposure head 10 (K, C, M, and Y) writes an electrostaticlatent image on the charged outer peripheral surface of thephotoconductor drum. The exposure heads 10 (K, C, M, or Y) are arrangedsuch that a plurality of organic EL elements are aligned along thegeneratrix (main scanning direction) of each of the photoconductor drums110 (K, C, M, or Y). The writing of an electrostatic latent image isperformed by radiating the photoconductor drums with light from theplurality of organic EL elements. The developing device 114 (K, C, M,and Y) deposits toner, serving as a developing agent, on theelectrostatic latent image to form a toner image, i.e., a visible imageon the corresponding photoconductor drum.

The black, cyan, magenta, and yellow toner images formed by the foursingle-color toner image forming stations are primarily transferred ontothe intermediate transfer belt 120 sequentially so as to be superposedonto one another on the intermediate transfer belt 120. As a result, afull-color toner image is obtained. Four primary transfer corotrons(transferring device) 112 (K, C, M, and Y) are arranged inside theintermediate transfer belt 120. The primary transfer corotrons 112 (K,C, M, and Y) are arranged in the vicinities of the photoconductor drums110 (K, C, M, and Y), respectively, and electrostatically attract thetoner images from the photoconductor drums 110 (K, C, M, and Y) totransfer the toner images onto the intermediate transfer belt 120passing between the photoconductor drums and the primary transfercorotrons.

A sheet 102 as a target on which an image is to be finally formed is fedone by one from a sheet feed cassette 101 by a pickup roller 103, and isthen sent to a nip between the intermediate transfer belt 120 abuttingon the driving roller 121 and a secondary transfer roller 126. Thefull-color toner images on the intermediate transfer belt 120 aresecondarily transferred onto one side of the sheet 102 collectively bythe secondary transfer roller 126, and then the transferred image passesbetween a pair of fixing rollers 127, serving as a fixing unit, to befixed on the sheet 102. Thereafter, the sheet 102 is discharged to asheet discharge cassette that is formed on the top of the image printingapparatus, by a pair of sheet discharge rollers 128.

Further, according to the above-described image printing apparatus,since the above-mentioned organic EL panels are used as the exposureheads 10 (K, C, M and Y), it is possible to meet demands for a reductionin the size of the exposure head. In addition, since the quality oflight emitted from the organic EL panel is hardly deteriorated, it iseasy to keep display quality for a long time.

FIG. 16 is a longitudinal sectional view showing another image printingapparatus using the above-mentioned EL panel as a line-type exposurehead. The image printing apparatus is a rotary-development-typefull-color image printing apparatus using a belt intermediate transfermethod.

In the image printing apparatus shown in FIG. 16, a corona chargingdevice 168, a rotary developing unit 161, an exposure head 167, and anintermediate transfer belt 169 are provided around a photoconductor drum(image carrier) 165.

The corona charging device 168 uniformly charges the outer peripheralsurface of the photoconductor drum 165. The exposure head 167 writes anelectrostatic latent image on the charged outer peripheral surface ofthe photosensitive drum 165. The exposure head 167, which is theabove-mentioned organic EL panel, is arranged such that a plurality oforganic EL elements are aligned along the generatrix (main scanningdirection) of the photoconductor drum 165. The writing of anelectrostatic latent image is performed by radiating the photoconductordrum with light emitted from the plurality of EL elements 14.

The developing unit 161 is a drum having four developing devices 163Y,163C, 163M, and 163K arranged at angular intervals of 90°, and isrotatable around a shaft 161 a in the counterclockwise direction. Thedeveloping devices 163Y, 163C, 163M, and 163K respectively supplyyellow, cyan, magenta, and black toners to the photoconductor drum 165to deposit the toners as developing agents on an electrostatic latentimage, thereby forming a toner image, i.e., a visible image on thephotosensitive drum 165.

The endless intermediate transfer belt 169 is wound around a drivingroller 170 a, a driven roller 170 b, a primary transfer roller 166, anda tension roller, and rotates around these rollers in a direction asindicated by arrow. The primary transfer roller 166 electrostaticallyattracts the toner image from the photoconductor drum 165 and transfersthe toner image to the intermediate transfer belt 169 passing betweenthis photoconductor drum and the primary transfer roller 166.

More specifically, during the first one turn of the photoconductor drum165, an electrostatic latent image for a yellow (Y) image is written bythe exposure head 167, a toner image with the same color is formed bythe developing device 163Y, and the toner image is then transferred ontothe intermediate transfer belt 169. During the next turn of thephotoconductor drum, an electrostatic latent image for a cyan (C) imageis written by the exposure head 167, a toner image with the same coloris formed by the developing device 163C, and the toner image is thentransferred onto the intermediate transfer belt 169 so as to besuperposed on the yellow toner image. While the photoconductor drum 165makes four turns in this way, yellow, cyan, magenta, and black tonerimages are sequentially superposed on the intermediate transfer belt169. As a result, a full-color toner image is formed on the intermediatetransfer belt 169. When images are formed on both sides of a sheet onwhich the images are to be finally formed, a full-color toner image isformed on the intermediate transfer belt 169 in such a manner that tonerimages with the same color are transferred onto the front and rearsurfaces of the intermediate transfer belt 169, and then toner imageswith the next same color are transferred onto the front and rearsurfaces of the intermediate transfer belt 169.

A sheet conveying path 174 is formed in the image printing apparatus toallow a sheet to pass therethrough. A sheet is picked up one by one by apickup roller 179 from a sheet feed cassette 178, is conveyed by aconveying roller along the sheet conveying path 174, and passes througha nip between the intermediate transfer belt 169 abutting on the drivingroller 170 a and the secondary transfer roller 171. The secondarytransfer roller 171 electrostatically attracts a full-color toner imagecollectively from the intermediate transfer belt 169 to transfer thetoner image onto one surface of the sheet. The secondary transfer roller171 is adapted to approach and be separated from the intermediatetransfer belt 169 by a clutch (not shown). When a full-color toner imageis transferred onto a sheet, the secondary transfer roller 171 isbrought into contact with the intermediate transfer belt 169. When atoner image is superposed on the intermediate transfer belt 169, thesecondary transfer roller 171 is separated from the intermediatetransfer belt 169.

The sheet having the toner image transferred thereonto in this manner isconveyed to the fixing unit 172, and then passes between a heatingroller 172 a and a pressure roller 172 b of the fixing unit 172, so thatthe toner image is fixed to the sheet. The sheet after the fixingprocess passes through a pair of sheet discharge rollers 176 to advancein a direction indicated by an arrow F. In a case of double-sidedprinting, after most of the sheet has passed between the pair of sheetdischarge rollers 176, the pair of sheet discharge rollers 176 arerotated in a reverse direction so that the sheet is introduced into aconveying path 175 for double-sided printing, as indicated by an arrowG. Then, the toner image is transferred onto the other surface of thesheet by the secondary transfer roller 171, and the fixing unit 172performs the fixing process on the toner image again. Then, the sheet isdischarged by the pair of sheet discharge rollers 176.

Since the above-mentioned image printing apparatus uses theabove-mentioned organic EL panel as the exposure head 167, it ispossible to meet demands for a reduction in the size of the exposurehead. In addition, since the quality of light emitted from the organicEL panel is hardly deteriorated, it is easy to keep display quality fora long time.

Although the image printing apparatus has been described as an exampleof the electronic apparatus including the organic EL device according tothe invention, the organic EL device according to the invention can alsobe applied to other electrophotographic image printing apparatuses, suchas an image printing apparatus that directly transfers a toner imageonto a sheet from a photoconductor drum without using an intermediatetransfer belt, an image printing apparatus that forms a monochromaticimage, and an image printing apparatus that uses a photoconductor as animage carrier.

1. A light-emitting device comprising: a substrate; a light-emittingelement which is arranged above the substrate and which has an anode, acathode, and an organic light-emitting layer interposed therebetween; afirst gas barrier layer that is formed of an inorganic compound andcovers a region larger than a region in which the light-emitting elementis arranged; and a second gas barrier layer that is formed of aninorganic compound and covers a region larger than the region in whichthe light-emitting element is arranged, the second gas barrier layer isdisposed on the first gas barrier layer, wherein a region in which thefirst barrier layer is disposed is not matched with a region in whichthe second barrier layer is disposed.
 2. The light-emitting deviceaccording to claim 1, wherein the region in which the first barrierlayer is disposed is larger than the region in which the second barrierlayer is disposed.
 3. The light-emitting device according to claim 1,further comprising: an organic buffer layer that is disposed between thefirst gas barrier layer and the cathode, a region in which the organicbuffer layer is disposed is larger than a region in which the cathode isdisposed.
 4. The light-emitting device according to claim 1, furthercomprising: a first organic buffer layer and a second organic bufferlayer that are disposed between the first gas barrier layer and thecathode, the second organic buffer layer is disposed on the firstorganic buffer layer, wherein a region in which the first organic bufferlayer is disposed is not matched with a region in which the secondorganic buffer layer is disposed.
 5. An electronic apparatus comprisingthe light-emitting device according to claim 1.